Control of electric motors.



No. 789,487. PATENTED MAY 9, 1905. W. E. CARPENTER.

CONTROL OI ELEGI'RIG MOTORS.

APPLICATION FILED OOT.10, 1904.

Witnesses:

UNITED STATES IVALTERE. CARPENTER, OF LY NN,

Patented May 9, 1905.

PATENT OFFICE.

.W'IASSACHUSETTS, ASSIGNOR TO GET- CONTROl; OF ELECTRlC IVlOTOFiSnSPECIFICATION forming part of Letters Patent No. 789,487, dated May 9,1905.

Application filed (litober 10, 1904. Serial No. 227,829.

To all whmn i'bm/rty concern:

Be it known that I, \VAL'DER E. OARIEN'IIGR, a citizen of the UnitedStates, residing at Lynn, in the county of Essex and State of Massachusetts, have invented certain new and useful Improvements in Control ofEkctric Motors, of which thefollowing is a specification.

This invention relates to a system of control of a shunt-Wound electricmotor; and its object is to provide means for running .such a motor atconstant speed.

A shunt-motor is commonly termed a constant-speed motor; but it is wellknown that varying the load on the motor causes a slight variation inthe speed of rotation. In some cases it is essential that a shunt-motordriving a machine should run at constant speed irrespective of the loadthereon-as, for instance, in machines having such delicate parts that avariation in speed might injuriously affect them or disturb their properoperation. As an example, a linotype-machine has a distributingmechanism which is exceedingly delicate, and for convenience andsimplicity a single shunt-wound electric motor is used to drive it andthe other parts of the machine. hen the load driven by the motor otherthan this distributing mechanism is thrown on or off, the speed of themotor, and hence the speed at which this mechanism is driven, woulddecrease or increase slightly unless some means were provided to preventit, and this variation in speed, on account of the delicate constructionof the mechanism,

is apt to cause imperfect operation or even break some of the parts. Inorder to obtain constant speed irrespective of the load on the motor, Iprovide a resistance and means by which it is cut into or out of thecircuit of the motor-armature as the load on the motor is thrown off oron, and so proportion this resistance that by cutting down the currentin the motor-armature it will exactly compensate for the change of speedwhich would result from coupling the load to or uncoupling it from themotor.

My invention therefore comprises a shunt- Wound electric motor, meansfor varying the load thereon, and means whereby the motor is run atconstant speed irrespective of changes in the load thereon. Other morespecific features of my invention will be definitely indicated in theclaims appended hereto.

The principles of my invention maybe embodied in many differentconstructions, depending on the arrangement of the parts of the machineand the character of the load driven by the motor. In many machines itis common to provide clutches for coupling portions of the load to ashaft driven by the motor. In sucha machine the movement of the parts ofthe clutch may be made to move the arm of a switch for cutting theresistance into or out of circuit, and thus keep the motor speed con- 5stant. In the accompanying drawings 1 have illustrated such aconstruction; but it must be understood that this is adopted merely forpurposes of illustration and that the principles of my invention may beemployed in construc- 7 tions widely different therefrom.

In the drawings, Figure l is an end elevation of the clutch and switch.Fig. 2 is a plan view of the same, showing the motor driving the parts.Fig. 3 is a back view of the clutch and switch. Fig. i is a section online as of Fig. 2. Fig. 5 is asection on line 5 5 of Fig.

4, and Fig. 6 is a diagram of the circuits.

Referring to the drawings, 1 indicates a sh unt-wound electric motordriving a-shaft 2, on which is keyed a pulley A belt 4-, running on thispulley, communicates rotary motion from shaft 2 to another shaft, andthus connects motor 1 to a load. Loose on the shaft 2 is a sleeve 5,having a pulley 6 thereon, and 5 a belt 7 runs on this pulley and apulley on another shaft, so that when sleeve 5 is coupled to shaft 2 anadditional load is thrown on the motor. On sleeve 5 are projections 8,and a clutch member 9, movable axially on shaft 2, is provided withprojections 10, adapted to cooperate with the projections 8. The end ofshaft 2 on which the clutch member 9 moves is slotted, and a pin 11 issecured to the clutch member and extends through this slot, so that 95member 9 turns with shaft 2, but is movable axially thereon. A pin 12 insleeve 5 extends into a groove in shaft 2 to prevent movement of thesleeve axially of shaft 2. In order to move member 9 into and out ofclutching relation to sleeve 5, an arm 13 is secured to the end of shaft2 in a manner permittingrotary motion of the shaft therein and extendsdownwardly therefrom. Atits lower end arm 13 is provided with a stud1a,which extends through an opening in anL-shaped piece 15, secured on astationary portion of the machine. A stud 16 or other suitable device isfastened to arm 13, by which the arm and the clutch member 9 may bemoved axially of shaft 2 to move the projections 10 out of or intoengagement with the projections 8.

Mounted on a block 17, secured to the machine, are switch-clips 18 and19, and a blade 20 is pivoted in the clips 18 and loosely connected toan arm 21, secured to the stud 14c. The armature 22 of the motor 1 isconnected in circuit through the clips 18 and 19 and blade 20, and aresistance 22 is connected be tween clips 18 and 19, so that when blade20 is out of engagement with clips 19 the armaturecircuit is completedthrough the resistance 22, and this resistance is short-circuited whenblade 20 enters clips 19.

The operation of the device as thus constructed will be readilyunderstood from the foregoing description. The motor 1 may be used todrive two independent machines or two parts of a single machine by meansof belts 4c and 7. The mechanism driven by belt 4 may be of delicateconstruction, requiring constant speed for perfect operation, and themechanism driven by belt 7 may be such that it is desired to start andstop it at intervals. As shown in Fig. 2 both mechanisms are coupled tothe motor 1. If itis desired to stop the parts driven by belt 7, theclutch member 9 is moved axially of shaft 2 by the stud 16 and arm 18 orby a pivoted lever connected to arm 13, thus moving projections 10 outof engagement with projections 8. This movement, however, carries theswitch -blade 20 out of engagement with clips 19, so that the armaturecircuit of motor 1 is completed through the resistance 22, which cutsdown the armature-current. The resistance 22 is so proportioned that thearmature-current is cut down just enough to compensate for the change inthe speed of rotation of the motorarmature which would be caused byuncoupling the load carried by belt 7 from the motor if the resistanceand switch were not used. To again start the mechanism driven by belt 7,clutch member 9 is moved forward again, projections 10 engageprojections 8, and sleeve 5 rotates with shaft 2. In doing this blade 20is moved into engagement with clips 19, resistance 22 isshort-circuited, and the normal current admitted to the armature 23. Thespeed of motor 1 therefore remains constant under all leads.

As above pointed out, the construction shown and described herein ismerely illustrative of the principles of my invention, and I do not wishto be understood as limited to this or any other specific embodiment ofmy invention. Also it is obvious that several cluches or equivalentdevices might be employed for connecting the motor 1 in driving relationto different machines or portions of a machine and each of theseclutches arranged to short-circuit a resistance in the armature-circuit.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. The combination of a shunt-wound electric motor, means for changingthe load driven theraby, and means for compensating for changes in theload to obtain constant speed of the motor.

2. The combination of a shunt-wound electricmotor, means for connectingit in driving relation to a load and disconnecting the load therefrom,and means whereby the motor is runat constant speed irrespective of theload thereon.

3. The combination of a shunt-wound electric motor, a clutch forchanging the load thereon, and means operated with said clutch tocompensate for changes in the load to obtain constant speed of themotor.

1. The combination of a shunt-wound electric motor, means for changingthe load driven thereby, andmeans whereby changing the load, changes theresistance of a circuit of the motor.

5. The combination of a shunt-wound elec tric motor, means for changingthe load thereon, and means whereby reducing the load cuts resistanceinto the armature-circuit of the motor.

(5. The con'ibination of a shunt-wound electric motor, a clutch forconnecting the motor in driving relation to the load and disconnectingthe load therefrom, a switch operated with said clutch, and a resistancein circuit with the motor controlled by said switch.

7. The combination of a shunt-wound electric motor, a clutch forconnecting the motor in driving relation to a load and disconnecting theload therefrom, a resistance in the armature-circuit of the motor, andmeans whereby operating the clutch to connect the load to the motorshort-circuits the resistance.

8. The combination of a shunt-wound elec tric motor, a clutch forconnecting the motor in driving relation to a load and disconnecting theload therefrom, a switch having a movable member connectedto the clutchand adapted to close the armature-oircuit of the motor, and a resistancein shunt to the switch.

In witness whereof I have hereunto set my hand this 6th day of October,1901.

\V ALTER E. CARPENTER.

\Vitnesses:

JOHN A. MoMANUs, Jr., Gnomes H. RYrINsKI.

TIO

